When a sensor of this type is subjected to acceleration, the test mass exerts a force on the vibrating element. This force changes the frequency of vibration in such a manner that the variation in the frequency of vibration of the vibrating element makes it possible to determine the acceleration to which the sensor is being subjected.
It is advantageous to have cells of small size. This presents the advantage of making them easier to install in the vehicles they are to equip.
Cells are thus known, in particular from document FR-A-2 739 190, that are made in the form of a plate in which etching is used to define the vibrating element, the support element, the test mass, and the link elements. Particularly compact cells can be obtained in this manner. They also enable a plurality of cells to be integrated in a common substrate, with the cells being made simultaneously so that the cost of manufacture can be relatively low.
Nevertheless, this desire for compactness is constrained by the fact that the dimensioning of the test mass influences the sensitivity of the sensor, the heavier the test mass, the greater the force exerted on the vibrating element.
In order to further reduce the size of cells of the above type while conserving a test mass of sufficient weight, attempts have been made to produce the cell in a thicker plate. Nevertheless that makes the plate more difficult to machine. In such cells, the extra thickness also leads to the sensing axis of the cell being inclined relative to a normal of the plate, thereby complicating installation of the cell in the vehicle that it is to occupy. The position of the sensing axis of the cell also depends on manufacturing variation.
Cells made in the form of a plate are also disclosed in document FR-A-2 813 122.